Gas permeability of poly(bis-trifluoroethoxyphosphazene) and blends with adamantane amino/trifluoroethoxy (50/50) polyphosphazene

Gas permeability coefficients of poly(bis-trifluoroethoxyphosphazene), (PTF EP) and its blends with adamantane amino/trifluoroethoxy polyphosphazene (P AdATFEP) containing adamantane groups on 50 mol% of the side chains were de termined at 35 degrees C, The PTFEP films prepared by both spin casting and solvent casting had the same permeability coefficients, within the precisi on of the measurements. PTFEP/PAdATFEP blends were phase-separated. Relativ e to pure PTFEP, gas permeabilities were reduced from 45 to 70% (depending on the penetrant) by blending 18.8 mol% of PAdATFEP with PTFEP. The permeab ility coefficients of low-sorbing, permanent gases (i.e. H-2, O-2, and N-2) decreased as penetrant size increased, suggesting that such polymers sieve these permanent gas molecules primarily based on penetrant size rather tha n penetrant solubility. Gas permeation properties of CO2 and hydrocarbon va pors did not change monotonically with penetrant size, suggesting an interp lay of gas diffusivity and gas solubility on overall gas permeability. Blen ding PAdATFEP with PTFEP increased gas selectivity. Ideal separation factor s of these PTFEP/PAdATFEP blends were significantly below upper bound value s, (C) 2000 Elsevier Science B.V. All rights reserved.